1. Field of the Invention
The present invention relates to an intake air rate controlling device for an internal combustion engine, which controls an intake air rate in response to driving conditions of a vehicle.
2. Discussion of Background
A throttle valve for an internal combustion engine for a vehicle is located in an air-intake passage of a throttle body, is opened and closed in proportional to a degree of operating an accelerator, and is operated upon a state of the vehicle, for example a detection of slippage and so on, as a rotational difference between a front wheel and a rear wheel, whereby the throttle valve controls an output of the internal combustion engine by controlling the intake air rate. Therefore, a structure for opening and closing the throttle valve is not such that the throttle valve is directly connected to an accelerator pedal and a linkage mechanism. Opening and closing positions of the throttle valve are operated by a motor and so on, and determined by a composite signal including a signal of an amount of operating the accelerator.
FIG. 4 illustrates a structure of a conventional intake air rate controlling device of an internal combustion engine. FIG. 5 is a cross-sectional view of the intake air rate controlling device illustrated in FIG. 4 in an axis direction of a throttle body. In the figures, numerical reference 1 designates the throttle body forming the air-intake passage 2, connected to an intake pipe (not shown) of the internal combustion engine. Numerical reference 4 designates a throttle valve substantially shaped like a plate, which is positioned in the throttle body 1 through a throttle shaft 3, supported by bearings 5 and 6, so as to be freely rotatable. The throttle valve 4 is constructed such that the intake air rate is controlled such that a passage area of the air-intake passage 2 is increased and decreased by a rotation, e.g. in a counter-clockwise direction in this figure, of the throttle shaft 3.
Numerical reference 7 designates a motor (a detailed structure inside the motor is omitted) for opening and closing the throttle valve. A motor shaft 8 is fixed to the motor, and a motor gear 9 is fixed to the motor shaft 8. The motor gear 9 is engaged with a reduction gear 11, supported by a pin 10 fixed to the throttle body 1, and the reduction gear 11 is further engaged with a throttle gear 12, which is fixed to an end of the throttle shaft 3, whereby a driving force of the motor 7 is transmitted to the throttle shaft 3. Numerical reference 13 designates a spring, engaged with the motor gear 9. The throttle valve 4 is stopped to have a low opening degree by a working torque of the spring 13.
Numerical reference 14 designates a rotor, fixed to an end of the throttle shaft 3. Numerical reference 15 designates a contactor, formed in the rotor 14. Numerical reference 16 designates a variable resistor for detecting a rotational angle of the throttle shaft 3. Numerical reference 17 designates a cover for fixing the variable resistor 16. An intake air supplied to the internal combustion engine flows through the air-intake passage 2 from a right hand to a left hand on a paper face of the FIG. 5 like narrow arrows.
In the next, an operation will be described, when a current is applied to the motor 7, the motor shaft 8 is rotated to drive the motor gear 9, the reduction gear 11, and the throttle gear 12, whereby the throttle shaft 3 is rotated. By the rotation of the contactor 15, located in the rotor 14, on the variable resistor 16, the rotational angle of the throttle shaft 3 is detected as an output value. To bring the output value from the variable resistor 16 to a target value, the current to the motor 7 is controlled in use of a control device (not shown) so that a torque of the motor 7 is in proportional to the working torque of the spring 13, and the angle of the throttle shaft 3 is controlled.
However, in the conventional intake air controlling device for the combustion engine, when a high rate of an air flows into the air-intake passage 2 under a state that the opening degree of the throttle valve 4 is large, in other words, a state that the throttle valve 4 is opened to have a small angle from a horizontal line, as illustrated in FIG. 5, a torque designated by a wide arrow in FIG. 5 is applied to the throttle valve 4 so as to close the throttle shaft 3 by a hydrodynamic force of the intake air. Because the throttle valve 4 is positioned in a flow of the intake air to have the small angle from the horizontal line, a difference of flow rate between an air flowing below the throttle valve 4 and an air flowing above the throttle valve 4 is caused in a manner similar to a principle of fly of airplanes, and a torque in a direction of closing the throttle valve 4 is applied to the throttle valve 4 by a pressure caused by the flowing rate difference.
Since the opening degree of the throttle shaft 3 is maintained by a balance between the torque by the spring 13 and the torque transmitted to the throttle shaft 3 from the motor 7 in the conventional intake air controlling device of the internal combustion engine, when the intake air rate has a pulse beat, the torque applied to the throttle valve 4 is largely varied by a variation of the hydrodynamic force, caused by a variation of a flowing rate.
On the other hand, as illustrated in FIG. 6, when the throttle valve 4 is positioned in parallel to a flow of the intake air, in other words the throttle valve 4 is fully opened, a torque applied to the throttle valve 4 becomes substantially zero. Accordingly, if the throttle valve 4 is moved little by any external force, a variation of the torque caused by the variation is also increased.
As described, there are problems that durability, reliability, and performances of the intake air controlling device are deteriorated by a large variation of the torque, applied to the throttle valve 4, as an outer disturbance in controlling the position of the throttle valve 4.
It is an object of the present invention to solve the above-mentioned problems inherent in the conventional technique and to provide an intake air rate controlling device, which can suppress a torque variation applied to its throttle valve, caused by a hydrodynamic force of an intake air, and has excellent durability, excellent reliability, and high performances.
According to a first aspect of the present invention, there is provided an intake air rate controlling device for an internal combustion engine comprising: a throttle body forming an air-intake passage, connected to an intake pipe of the internal combustion engine; and a throttle valve in a plate-like shape, supported to the throttle body through a throttle shaft so as to be rotatable, wherein an air-intake rate, supplied to the internal combustion engine, is controlled by a rotation of the throttle valve,
wherein the intake air rate controlling device further comprising an air-flow controlling means for suppressing a variation of a torque caused by a hydrodynamic force generated by an intake air and working on the throttle valve.
According to a second aspect of the present invention, there is provided the intake air rate controlling device, wherein the air-flow controlling means is located within an area of the height of the throttle shaft.
According to a third aspect of the present invention, there is provided the intake air rate controlling device, wherein the air-flow controlling means is shaped like a wing having a slant with respect to an axis line of the throttle body.